Switching control system



NOV. 3, 1953 1 R, NEUBAUER 2,658,172

SWITCHING CONTROL SYSTEM Filed Sept. 20, 1951 l INVEN-roR T :1I-m RNEUBHUEH ATTORNEY Patented Nov. 3, 1953 SWITCHING CONTROL SYSTEM John R. Neubauer, Collingswood, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 20, 1951, Serial No. 247,532 Claims. (Cl. 317-141) This invention relates to a control system for a radio transmitter, and more particularly to a control system for an unattended radio transmitter such as might be used in mobile communications equipment.

Generally, a mobile communications system may include one or more remotely located, unattended radio transmitters which are controlled to radiate a carrier in response to the operation of a push-to-talk switch at the point where the desired intelligence is originating and which, when so controlled or energized, function to relay or repeat the intelligence to a distant point. Such unattended radio transmitters are controlled by a sensitive control relay which may be energized by received carrier energy derived from a radio receiver or by a direct current telephone line relay, said sensitive control relay in turn acting to energize the plate power relay of the controlled transmitter to cause such transmitter to radiate carrier energy which may then be modulated by the intelligence to be relayed.

On some occasions, the sensitive control relay at the transmitter may fail to deenergize or it may become energized in response to control signals not originated by the normal controlling source. The failure or improper functioning of the control relay may not be permanent or of such a nature as to require repair. For example, the carrier-operated relay could become continuously energized in response to a spurious signal being radiated by a diathermy device or in response to harmonic radiation from a nearby broadcast transmitter, or the telephoneline-controlled relay could be continuously energized in response to a spurious voltage as a result of a shorted lor leaking telephone cable. Thus, the control relay at the unattended transmitter may become continuously energized due to circuit failure or to a spurious control signal, and if this occurs such transmitter will continuously radiate carrier energy.

Continuous uncontrollable radiation of carrier energy by a transmitter, which cannot be stopped by the operator at the dispatching or control point, is undesirable in radio communication systems having several other units operating on the same channel, since such continuous radiation of the carrier renders it very diicult, if not impossible, for these other units to operate properly. Also, if the transmitter is part of a chain of relay or repeating stations, continuous radiation would disable all units. Then too, the transmitter may be located at a point which would require considerable time to travel to, in order to remedy improper control relay functioning thereat; this can be a large factor in systems located in large undeveloped areas. For all of the above reasons, it is highly advantageous to utilize an arrangement at an unattended controllable radio transmitter, which will prevent such a transmitter from continuously radiating due to failure of the control device or due to control signals not originated by the normal controlling source.

An object of this invention is to devise a novel automatic control circuit for a transmitter, which will limit the time interval that such transmitter can continuously radiate carrier energy.

Another object is to provide a circuit which will prevent an unattended radio transmitter from continuously radiating carrier energy in response to abnormal causes, but which will automatically restore the transmitter to service if the abnormal causes cease to exist or are removed.

A further object is to devise a control circuit condition sampling device which at the end of a 1- predetermined time interval determines whether or not the control circuit is normal, and then goes on to produce different results corresponding to thenormality or abnormality of the control circuit.

The foregoing and other objects of the invention will be best understood from the following description of an exempliiication thereof, reference being had to the accompanying drawing, wherein the single figure is a schematic representation of a circuit according to this invention.

Briefly, the objects of this invention are accomplished in the following manner: A circuit condition sampling device, including a timer, allows a predetermined interval of time to elapse from the initiation of transmission by a transmitter, at the end of which interval the device determines, by means of a relay circuit, whether the transmitter control circuit is normal. If such circuit is normal, the sampling device resets for a new cycle without interrupting any control functions of the transmitter. Should the control circuit be locked on at the end of this interval, however, the sampling device interrupts the circuit of the transmitter plate voltage relay and maintains the transmitter off until the control circuit is released.

Now referring to the single figure of the drawing, the relay l is a sensitive control relay located at the unattended radio transmitter, at which all of the circuitry illustrated in the figure is located. As indicated in the drawing, relay I may be energized either by a carrier-responsive energization circuit or a telephone-line-controlled energization circuit. In either case, push-to-talk or manual operation by the station operator at a remote point causes energization of :relay I.. If thecontrol path Jbetween the remote `point 'and the yunattended transmitter is a radio carrier link, in which case the energization of relay l is effected in response to the presence of a carrier at the unattended transmitter, a relay energization circuit such Eas disclosed -in my co-pending joint application, Serial .No

222,504, iiled April 23, 1951, may -be used. 1f the control path between the remote point and the unattended transmitter is a telephone line, a high resistance direct current Vrelay may `he `used for energization of relay I, this` directl current relay being connected at 'the terminating (transmitter) end of the telephone line, between the center Ltaps oi the line-.terminating transformer. ln this case, the Arcmoitecontrol unit would apply ,a unidirectional potential from -the remote control point, which potential would vtravel down `the two sides of the line .and energize the .direct current relay. This latter .relay would then, in turn, energize the .sensitive 'relay 'I of the transmitter.

When the relay I is energized 'in response 'to .a Amanual operation by the operator at .the .remo'te operating point, its normally-open .contacts 2 are closed to connect .the coil of ,relay 3 across the two buses 4.and 5., which are supplied from a suitable source (not shown) of control relay voltage, bus 4 .being .connected to one terminal of such source and "bus '5 being connected to the other 'terminal thereof. '.Bus '5 kmay -be grounded, Y,as shown. Buses 4 and `5 maybe supplied with either alternating or direct current, as `'dictated `b,y design considerations. In atypical example, these 'buses were connected to opposite sides of a ..6.3-volt, alternating current source. When contacts 2 are closed, `relay )3 Lis energized to .close 'its three .pairs of normally-open contacts 6, `1 and 8. Closure of contacts "I Ycompletes a circuit "through contacts 9 .and '.I0 (which contacts are normally closed in thepos'itions .illustrated and in such positions are 'in parallel with each other) from bus A through the coil of relay 'il 'to "bus '5, thus energizing relay `I I.

Energization of .relay -II closes y.its .normallyopen contacts I2., which are in series inthe plate 'energization .circuit of lthe transmitter.; 'this applies ,plate voltage vto the transmitter, causing yit to radiate carrier energy. Thus, energization of relay I normally causes energization of the transmitter through energization o'f relay 3.; the normal carrier-.on and .carrier-ofi' control func,- tions in the transmitter vare thus transferred from .the relay I to the relay v3.

'Closing of contacts "6 .of relay '3 causes energiza'tion of .relay I3 "through anv obvious circuit, relay I3 'then closing its two pairs of normally- 'open contacts I'll and I5. 'Closing 'of contacts I4 (one 'of which is connected to the Aupper end vof the coil of .relay I3) completes a circuit through the "normally-closed contacts I'B of relay I'I to bus 4, thus providing .a 'holding 'circuit for relay I-3, independent of contacts 6, 'as follows: 'bus 5, coil of relay I3, closed contacts I`4, closed contacts IB, bus 4.

Closing of contacts I5 of relay :I3 completes an-fobvious circuit from the H5-volt alternating .current `source 12,0 to the adjustable reset timer 118, Ato start this timer or ti-ming clock. An adjustable reset timer is designed to complete any preset time interval (five minutes for timer I8), at the end of which it operates a switch and holds the same in its operated position as long as alternating current is applied to the timer. The switch operated by timer I8 is the singlepole double-throw switch I0, which is illustrated iiniits sunoperated position :In its operated position, the movable arm 4of .switch .I-0 engages its lower xed contact and is spaced from its upper fixed Contact. When the alternating current is removed from the timer, the holding clutch in the vtimer releases and the timing mechanism :returns to its original position, restoring the vswitch toits normal unoperated position illustrated.

Since relay I3, once it is energized, remains 'energized through its own holding circuit irrespectifve oi any subsequent de-energization of relays I and 3, reset timer I8 will run continuously to the end of its five-.minute cycle .(.the given interval of time of 'the circuit condition vsampling arrangement), at which time switch .Il is operated by said timer to open its upper .'fixed contact and close vits lower fixed contact. The opening of the upper contact o'f I0 .will ibut only .if the `parallel contacts '9 are also .open at this time) interrupt the circuit 'to the 'transmitter plate voltage relay I I, thus `Cle-energizing the transmitter. lThe .closing of the .movable arm of i0 on its lower contact completes an `obvious circuit to the coil of relay `I.'I energizing this relay and opening its normally-closed .contacts IB.

If the control circuit including .relays I 'and 3 isinormal at this time, that is, if `thesensitiye control relay I is not 'holding relay .3 closed, the holding circuit .of relay I3 .is broken at .contacts I6 and relay I3 is cle-energized .to open .its oon.- tacts i4 and I5. The opening of contacts lI`.5 breaks the circuit 'from the alternating .current sourceto .reset the timer 1:8, removing the voltage from this timer so that switch I0 is restored to its normal, original, illustrated position. Closing of the arm 'o1' switch IIJ on its upper contact re- `stores this portion Y(through contacts Ill, which are in parallel with contacts 91) .of ithe circuit .to the transmitter plate voltage .relay Il., while opening Vof the lower contact of 'Ill de-,energizes relay iII to re-'establish the holding circuit 4for relay 13.

Thus, if the control circuit is normal, .the sampling circuit of this invention resets .for a new cycle without interrupting any .controlfunc- 'tions ofthe transmitter (it will be recalled that these control 'functions are effected mainly 'by way of relays I and 3).

If `the control circuit is locked on, however, that is, .if the 'control relay "I continues to hold relay 3 lenergized at the end of the cycle of .timer i8, which occurs five `minutes after relay I3 llirst closes its contacts 15, relay I3 is not released or de-energized by the opening of contacts "I6 at this time as a result of energization of relay Il, but is held Aclosed through closed contacts ll o'f relay 3. 'Contacts I5 then remain closed .and holdthe reset `clutch of .timer I8. This will maintain the open 'circuit to the .transmitter plate voltage relay -I i through the openupper contact of I0, timer I8 'holding switch ID in .its .operated position -until `such time as the relay I releases relays 3 and -I3 to open contacts I5 lso that vtimer `Ill can lreturn switch I0 to its 'unoperated, illustrated position. Contacts 9 are 'open at this time, since the reset clutch of `timer I9, which operates these contacts, -is held through closed contacts 8 of relay 3. Plate voltage relay II is eiectively open-circuited under these conditions.

Thus, if the control circuit is locked on the sampling circuit of this invention interrupts the energization circuit of the plate voltage relay and maintains the transmitter off until the control circuit is released.

In order to provide for uninterrupted carrier transmission, should the operator initiate a new transmission prior to the end of the five-minute timing cycle of limiting timer I8, an additional shorter interval adjustable reset timer I9 is cycled with each operation of relay 3 through its contacts 8, which when closed by relay 3 connect timer I9 to the alternating current source. Timer I9 may have a time interval of one minute, for example. Timer I9 controls contacts 9, which in their normal unoperated illustrated position are closed and in parallel with the normal unoperated illustrated position of contacts Iii. Since timer I9 is cycled (started) with each energization of relay 3, the circuit of transmitter plate voltage relay II is maintained through closed contacts 9 for a denite time (a maximum of one minute, the timing interval of timer I9) from the begin ning of each transmission cycle, the timer I9 being reset (and contacts 9 being returned to the closed position, in the event they have been opened) at the end of the transmission cycle by the opening of contacts 8 of relay 3.

Thus, the operator might initiate a new transmission from the unattended transmitter shortly (one minute or less) before the end of the veminute timing interval of timer I8; even though the timer I 8 opens the upper contact of switch I0 at the end of its timing interval, the circuit to plate voltage relay I I will be maintained through contacts 9 and the transmitter will radiate carrier uninterruptedly, provided of course that the length of this new transmission is one minute or less from the time that relay 3 is energized to start transmission and to cycle timer I9, since one minute after transmission starts timer I9 finishes its cycle and opens its contacts 9, if contacts 8 are closed at that time. In standard mobile communications practice most transmissions without the carrier being interrupted are for reasonably short intervals (such as 45 to 50 seconds), so that the one-minute time interval of timer I9 (before its contacts 9 open) allows ample leeway for transmissions at times which overlap the end of the live-minute timing cycle of timer In the event of a locked control circuit (where relays I and 3 have become continuously ener gized due to circuit failure or to a spurious conn trol signal not originated by the normal controlling source), timer I9, since it has a timing interval of only one minute, will open its contacts 9 considerably ahead of the opening of contacts I by timer I9. In the locked control circuit case, contacts 8 are of course closed so that timer I9 opens its contacts 9 one minute after the closure of contacts 8. Under locked control circuit conditions, therefore, contacts 9 are open long before the end of the cycle of timer I8, which occurs ve minutes after relay I3 rst closes its contacts I5. `Contacts 9 being open at the end of this ve-minute given interval, the plate voltage relay II is effectively open-circuited, de-energizing the same and turning off the transmitter, when timer I8 opens the upper contact of switch I0. The carrier-off or transmitter-off condition is then maintained until the control circuit, vincluding relays I and 3, is released to de-energize such relays. `The opening oi contacts 8 of relay 3 resets timer I9 to close its contacts 9 and set up a circuit through the coil of plate power relay II, while the opening of contacts 1, of course, positively breaks the circuit through such coil. The opening of contacts 6 causes de-energization of relay I3 and the opening of its contacts I5 to reset the timer I 8, since at this time (subsequent to the end of the timing cycle of timer I8) switch I0 is closed on its lower contact to energize relay I'I and open contacts I6. When timer I8 is reset, switch I0 is again closed on its upper contact to set up a parallel circuit through the coil of relay I I.

Ii contacts 9 of timer I9 are closed because of a desired transmission at the end of the veminute sampling cycle (when timer I8 operates switch I0), in which event relays I and 3 are of course energized, the sampling device I8, I0, I6, etc. interprets this as a locked on condition of the control circuit. Relay I3 is then not de-energized to reset timer I8 but is held closed through closed contacts 6 of relay 3, as long as relay 3 is energized. When relay 3 is released or de-energized at the end of the desired transmission, opening of its contacts 6 causes deenergization of relay I3 to open its contacts I5, resetting timer I8. At the same time, the opening of contacts 1 of relay 3 de-energizes the transmitter power relay II and the opening of contacts 8 of this relay resets timer I9.

Of course, if the desired transmission lasts long enough after the end of the Eve-minute sampling cycle for the timer I9 to complete its one-minute timing period, contacts 9 of timer I9 are opened and, since the upper contact of switch I0 is then open (timer I8 having completed its timing period and the contacts I5 of relay I3 being closed, relay I3 still being energized through closed contacts B), the transmitter plate relay II will be positively de-energized and the transmitter cut off, even though contacts 'I of relay 3 are still closed. In this latter event, the transmitter will remain off, and the relays and timers will not be reset, until relays I and 3 are de-energized at the end of the desired transmission.

It is desired to be pointed out that, with the circuit of this invention, it is impossible to have a single continuous transmission longer than the five-minute timing period of timer I 8. Under continuous transmission conditions of this length, relay 3 would be energized (and its contacts 8 closed) so that contacts 9 of timer I9 would be open, timer I9 having completed its one-minute timing period. ySince contacts 9 are then open, contacts I0 of timer I9 would denitely open the circuit to transmitter relay II at the end of the five-minute timing cycle of timer IB, even though contacts l of relay 3 are still closed.

However, this five-minute limitation on continuous transmission is not important in mobile communications, for which the circuit of this invention is particularly adapted, since in such communications there is never any continuous transmission lasting that long. The circuit of this invention is particularly suitable for use in the general iield of mobile communications for the protection of unattended remotely located transmitters, where there is no need for longsustained continuous transmission. Considering the fact that in standard mobile communications practice most communications last from 45 to 50 seconds maximum without the carrier being interrupted, one of the unique features of :this invention is that the circuit 'is automatically freset to sample ,a new cycle `(by the normallyoocurring .release .of relay -Ii3 fand resetting of `timer 1h82) .at 'the end lof a :five-minute lperiod which may cover :a fgroup fof transmissions, ve *minutes being the ltiming interval of timer 1'8. In standard press-to-talk communication fpractice, Isubstantially continuous transmissions of :more than veminutes could be effected With 'the vcircuit y.of this invention yby a :momentary re- .lease of :the control `.circuit fjust prior to `the con- -clusion 'of the dive-minute sampling period, thereby establishing va new sampling cycle at the endl'of :the rive-.minute sampling period :through the release of relay I3 and resetting ,of timer I8.

:Itzshould ybe undertsood that "the invention -may -be 'fused in any field :of communication l(except where continuous transmission exceeding ve Aminutes isadesi-red) whereit is 'desired to prevent iuna'ttended radio transmitter 4from continul.ously operating .'due 'to failure of a control :de-

vice .vor to control signals vnot originating at the 'normal controlling fsource.

=,Generally,=the relays -I and I I constitute part of .a transmitter -With which the invention r(consisting fof ythe :remainder of the relay Acircuit illus- 'trated is to Ibe used. In this case, of course, the icoil 'voltages `and frequencies tot relays 3, I- Aand Iflgshould be thesame-as those of the coil of plate power relay IfI so that the -same common source yof :relay Avoltage can "be fused vfor all relays, with the possible exception of relay I. For timing vpursposes, .obviously the alternating current source 20, ywhich supplies -power to timers I8 .and I9,

.should .be the standard SO-cycle commercial Isource.

What lis claimed is:

1. .In -a systemffor venergizing ia controlled device latalocation, .a nrst relay, a-circuit 'or causing energizationnf :said tirelay in response to the jpresence of a .signal at fsaid location iand for causing 'de-energization fof 4said relay :in yresponse ato the yabsence of -a sig-nal thereat, ia 'second re- .lay ,adapted to 'be energized in response yto the V'energization of :said rst relay, a time interval `measuring device connected :to be energized .in response to `the yenergization of said second relay, 'a pair 'of :normally-closed contactscontrolled .by :said measuring device, :said contacts `being -opened by :said measuring device :at the end of Ithe timeinterval measured thereby, a third relay ffor Yenergizing :said (controlled device, an .ener- -gization circuit 'for said third reiayincluding in fseries said pairo'f contacts and 7a ,-pair of contacts closed -by .the energization `of fsaid rst relay, ta

holding Vcircuit 'for -said second relay including in series -a pair of contacts closed ,by the -energization of lsaid second irelay 'and a A.pair of normalty-closed contacts, and means operated vby said measuring device lat the end of its :time `interval for 'causing opening of 'said last-named ipair fof `contacts.

'2. in a system 'for .energizing `a controlled device at a location, a first relay, a circuit 'for caus- -ing-.en'ergization l'of .said relay 'in response to the presence of a signal .fat vsaid location and for 'causing de-'energization Yof said relay Vin response :to the absence `of a signal thereat, a 4'second revlay adapted -to `be energized in response to the .energization of said ii-rst relay, a rst time intervalfm'easuring device connectedto be energized in response tto the energization of saidfsecond relay, .a pair .of normally-closed contacts -controlled .by .said measuring device, said f4contacts being vnpened Aby said :measuring kdevice-'at the endof the time interval .measured thereby, a :second iti-me interval measuring device `connected to be Lenergized in response to the energization of said `first relay, the `time :interval V.measured fby .said second measuring device .being Shorter than that measured by said efrst measuring device, Aa `pair of normally-closed 'contacts controlled :by said second measuring device, `'said last-named contacts being Aconnected in parallel with the .firstv.named `contacts vand being opened by rsaid :second rmeasuring device at the :end of the :time .interval measured thereby, a third `relay ifor energizing said :controlled device, an 4energization circuit :for said third relay including *the parallel combination of `'said rst-named and .second-named contacts .in tseries with :a pair ,of contacts closed 'by the energiza'tion of said first relay, bet-Ween .a source and said fthirdrelay, Ja holding circut'ior 4said .second relay including in series a Lpa'ir fof contacts closed by the energization :of ,said secondirelay and a pair of normally-closed contacts, andmeans :operated fby Said first measuring device fat the vend of its time interval for causing ropening of said last-named 'pair :of contacts.

3.. VIn asystem'for energi-zinga:controlled device rat a location, a liirsttrelay, `a circuit for `causing energization of fsaid .relay in vresponse #to "the presence of asignal at Tsaid llocation vandforfcausing de-energization of said relay in response ito the absence of a signal 'thereatia .second relay, an energization circuit for said Asecond :relay which is completed in vresponse lto theenerglizaltion of :said first relay, `a time :interval measuring device, means responsive to 'the 4energizetion lof Ysaid second relay vfor causing energize.- tion of said measuring device, fa pair :of normally-closed contacts controlled by :said measuring device, 'said contacts rbeing :opened 'by fsaiil measuring ydevice at .the 'end of the time inter-- V4val measured thereby, fa third relay lf'or lener- :giizing'said controlled device, an energlization-cir- 'cuit for said third relay including 'in series said pair of `contactsand a .pair of :contacts :closed by 'the fenergization 'of Asaid first relay, a fourth relay having a'vpair `of .normaity-closedcontacts, .a -holding circuit for said second relay including in series a pair vof contacts :closed `by 4.the `enertgization lof said 'second relay :and the contacts of saidIQurthrelay, andfanenergization circuit for said `fourth `relay completed by the ,operation Iof `saild measuring-device `at the end Yof its `time interva 4. In a .system for energizing 'a controlled 4device at a location, a rst relay, a circuit for causing energization fof 'said .relay in response 4to ithe `presence of fa 'signal kat 'said .location land ifor causing de-energization oisai'd relay .in'response .tothe `absence of a -signal thereat, a .'secon'd irelay, an energization circuit for "said second relay which is completed in response to the energizetion of vsaid rst relay, a rst Vtime interval measuring device, means responsive to the energiza'tion of said second relay fior causing energization of said measuring device, a pair of normally-closed contacts controlled by said measuring device, vsaid rcontacts being opened 'by ysaid Ameasuring device -at the end of the time interval measured thereby, a `second time interval rmeasurng device, V4means yresponsive to the energizeltion of said rst relay for `causing"energization df said second v:measuring device, the time interval measured by said second measuring device being shorter than that measured by saidrst measuring AAdevice, a -pair of normally-closed Econtacts controlled by said secondmeasuri-ng device, :said

last-named contacts being connected in parallel with the rst-named contacts and being opened by said second measuring device at the end of the time interval measured thereby, a third relay for energizing said controlled device, an energization circuit for said third relay including the parallel combination of said rst-named and second-named contacts in series with a pair of contacts closed by the energization of said first relay, between a source and said third relay, a fourth relay having a pair of normally-closed contacts, a holding circuit for said second relay including in series a pair of contacts closed by the energization of said second relay and the contacts of said fourth relay, and an energization circuit for said fourth relay completed by the operation' of said first measuring device at the end of its time interval.

5. In a system for controlling` an electrical device. a two-condition electrical-signal-responsive controlling means responsive to an electrical signal effective thereon for controlling the device in one or the other of two opposite senses corresponding respectively to each of said two conditions, means responsive to the operation of said controlling means to one of said two conditions for measuring a predetermined time interval beginning at the instant of initiation of control in said one sense of said device by said controlling means, and switching means controlled by said measuring means for sampling the condition of said controlling means at the end of said time interval and for operating to control said device in said other sense if said controlling means is in one condition when sampled and for operating to reset itself and also said measuring means if said controlling means is in the other condition when sampled.

6. In a system for energizing an electrical device, a two-condition electrical-signal-responsive controlling means for controlling the device, said means being placed in a i'irst condition for energizing said device in response to the presence of an electrical signal and being placed in a second condition for de-energizing said device in response to the absence of an electrical signal, means responsive to the placing of said controlling means in said rst condition for measuring a predetermined time interval beginning at the time of energization of said device by said controlling means, and switching means controlled by said measuring means for sampling the ccndition of said controlling means at the end of said time interval and for operating to (le-energize said device if said controlling means is in said first condition when sampled and for operating to reset itself and also said measuring means if said controlling means is in said second condition when sampled.

7. In a system for controlling an electrical device, a two-condition electrical-signal-responsive controlling means responsive to an electrical signal effective thereon for controlling the device in one or the other of two opposite senses corresponding respectively to each of said two conditions, a iirst means responsive to the operation of said controlling means to one of said two conditions for measuring a predetermined iirst time interval beginning at the first initiation of control in said one sense by said controlling means, a second means responsive to the operation of said controlling means to said one condition for measuring a smaller predetermined second time interval beginning at the instant of each initiation of control in said one sense by said controlling means, and switching means controlled by said iirst measuring means for sampling the condition of said controlling means at the end of said iirst time interval and for operating to control said device in said other sense if said controlling means is in one condition when sampled and if said second measuring means has measured out its time interval when sampling occurs and for operating to reset itself and also said rst measuring means if said controlling means is in the other condition when sampled.

8. In a system for energizing an electrical device, a two-condition electrical-signal-responsive controlling means for controlling the device, said means being placed in a iirst condition for energizing said device in response to the presence of an electrical signal and being placed in a second condition for de-energizing said device in response to the absence of an electrical signal, a irst means responsive to the placing of said controlling means in said first condition for measuring a predetermined first time interval beginning at the time of a rst energization of said device by said controlling means, a second means responsive to the placing of said controlling means in said iirst condition for measuring a smaller predetermined second time interval beginning at the time of each energization of said device by said controlling means, and switching means controlled by said first measuring means for sampling the condition of said controlling means at the end of said iirst time interval and for operating to de-energize said device if said controlling means is in a said first condition when sampled and if said second measuring means has measured out its time interval when sampling n if said controlling means 1s in said second condition when sampled. 9. In a system for energizing an electrical deof an electrical signal and being placed in a second condition for tie-energizing said device in response to the absence of in response to the placing of said controlling means 1n said rst condition, whereby said measis in said first condition when sampled and for operating to reset itself and also said measuring means if said controlling means is in said second condition when sampled.

10. In a system for energizing an electrical device, a two-condition electrical-signal-responsive controlling means for controlling the device, said means being placed in a rst condition for energizing said device in response to the presence of an electrical signal and being placed in a second condition for deenergizing said device in response to the absence of an electrical signal, a first means for measuring a predetermined rst time interval beginning at a certain instant, circuit means controlled by said controlling means for 111. causing energizationof said measuring, meansin` response to a first placing` of said controlling` means in said. rstcondition. whereby said meas,-` uring. means measures its. time interval from the instant of a first energization of said device by said. controlling means, a secondmeansfor meas.- urng; a. smaller predetermined second. time in-.

terval. beginning at` a certain instant, circuit.

means -controlled by said controlling meansv for causing energization oi said` secondy measuring means in responseto.` each placing of said con,- trolling; means in said:r irst condition, whereby said second, measuring meansmeasures its time interval frornf the instant of each energization of said device by said. controlling means, and switch-` ing'. mean-s; controlled; by lsaid lirstv measuring-A means for' sampling.` the. condition of saidl controlling; means. at. the, endI of said firstl time inrtcrval` and or operating to. deenergize saidde 12? vice: if sai-d` controlling: means. is in said; first. condition, when sampled. and. if. saidsecondi Ineas uringmeans has measured outits timeinterval'e when. sampling occurs; and for operating tof ner set. itself and, alsoV said rstmeasuring meansu; saidi controlling meansis in saidi second', condition.l when sampled;

JOHN R.. NEUBAUER.

References.: Citedl inA the le.- of this. patent., UNITED STATES PATENTS Number. Name. Date.

1,342,635 Lewisv June 8; 1920i` 1,763,390. Davis June 10;,1Q3L0" 2,083,849, Litstrorn- June` 15;,11837." 2,094,733.' Byrnes. Oct.. 5,i 133.7.' 2,339,750 Bartholy Jan. 25.19.4142, 

